Compositions for dissolution of low-k dielectric films, and methods of use

ABSTRACT

An improved composition and method for cleaning the surface of a semiconductor wafer are provided. The composition can be used to selectively remove a low-k dielectric material such as silicon dioxide, a photoresist layer overlying a low-k dielectric layer, or both layers from the surface of a wafer. The composition is formulated according to the invention to provide a desired removal rate of the low-k dielectric and/or photoresist from the surface of the wafer. By varying the fluorine ion component, and the amounts of the fluorine ion component and acid, component, and controlling the pH, a composition can be formulated in order to achieve a desired low-k dielectric removal rate that ranges from slow and controlled at about 50 to about 1000 angstroms per minute, to a relatively rapid removal of low-k dielectric material at greater than about 1000 angstroms per minute. The composition can also be formulated to selectively remove a photoresist layer, leaving the underlying low-k dielectric layer essentially intact.

FIELD OF THE INVENTION

[0001] The present invention relates to compositions and methods fortheir use in cleaning or etching of wafers used in tire fabrication ofsemiconductor devices. More particularly, the invention relates tocompositions for selectively removing low-k dielectric layers and/orphotoresist layers on the wafers while controlling the rate of removalof the material, and methods using the compositions.

BACKGROUND OF THE INVENTION

[0002] Many semiconductor processes require wafer measurements to bemade from time to time for production-line quality control, productstability, and conformance to specifications. Generally, the processingresults are evaluated after each significant step. Since many tests aredestructive or will harm the product wafer, the measurements aretypically performed on a test or “dummy” wafer, which are blank wafersthat are mixed in with the product wafers. Dummy wafers are speciallyprepared to have similar characteristics as the product wafers.Typically, a dummy wafer is made of silicon, although other alternativematerials have been described. Since silicon wafers are expensive, whenthe processing and testing is completed, the dummy wafers are usuallycleaned, inspected, and reused. In the recovery or recycling of dummywafers, it is important to provide a clean surface for subsequentprocessing. In the recycling of dummy wafers used in a maskingphotoresist process, it is important to completely remove blanket filmsof oxide and resist layers from the surface of the wafer down to thebare silicon.

[0003] Wet chemical processing is conventionally used for cleaning thesurfaces of wafers. The cleaning is performed in order to produce awafer having a silicon surface that is hydrophobic and repels water asthe wafer is pulled out of the bath. The wafers are then rinsed indeionized water, dried in heated nitrogen gas (N₂), and transferred to aprocessing operation, or stored.

[0004] Aqueous mixtures of hydrogen peroxide (H₂O₂) and sulfuric acid(H₂SO₄) are commonly used to strip or remove photoresist from a wafersurface after an etch processing step, or to remove a misaligned resistpattern from a wafer for re-imaging after development and inspection(“rework”). In such applications, it is desirable that the layer that ispresent under the resist, including, for example, silicon dioxide,remains intact on the wafer surface. In such cases, it is important toquickly remove the photoresist layer without attacking the underlyingmaterial. However, organic components in an underlying low-k dielectriclayer, can alter the selectivity of the dielectric material to a resistlayer.

[0005] In other applications, it is desirable to completely remove theoxide layer from a silicon surface. Hydrofluoric acid (HF) isconventionally used as a component of oxide etchants. HF solutionsprovide selective etch rates of about 100:1 or better for SiO₂:Si, andeffectively etch away the oxide but not the underlying silicon wafermaterial. Prevalent HF solutions include, for example, a 1:10 mixture of49% hydrofluoric acid (HF) and water, and a dilute 1:6 aqueous mixtureof HF and ammonium fluoride (NH₄F). However, wet HF chemistries havedifficulty removing low-k dielectrics such as a TMS-based low-kdielectric film, largely due to organic components in the oxide films.As a result, cleaning with an HF solution can leave the wafer with agummy organic residue on the surface.

[0006] Therefore, it would be desirable to provide an improvedcomposition for dissolution of low-k dielectric films fromsilicon-comprising surfaces. It would also be desirable to provide acleaning composition that will completely remove low-k dielectric andphotoresist components from the surface of a substrate such as a dummywafer. It would also be desirable to provide a composition that can bemodified to provide removal of a low-k dielectric material such as aTMS-based low-k dielectric film, from a wafer surface over a range ofremoval rates according to the application at hand.

SUMMARY OF THE INVENTION

[0007] The present invention provides a cleaning composition for use inwet cleaning or etching of a wafer surface, and a method of cleaning oretching wafer surfaces by applying the composition.

[0008] The cleaning composition is an aqueous solution that includes oneor more effective amounts (v/v) of one or more fluorine-comprisingcompounds and one or more compatible acids to achieve the desiredselectivity to resist and/or a low-k dielectric, and the desired rate ofremoval of the low-k material and/or the resist. A preferred compositionaccording to the invention is an aqueous solution consisting essentiallyof the one or more fluorine-comprising compounds and the one or moreacids.

[0009] The cleaning composition can be modified according to theinvention to provide removal of a low-k dielectric material from thesurface of a semiconductor wafer or other substrate over a range ofremoval rates according to the application at hand. In particular, thefluorine-comprising compound and the amount that is used, and also theamount of the acid component that is used, can be varied according tothe invention to provide rapid removal of a low-k dielectric materialand/or organic materials such as photoresist from the surface of thewafer at a rate of removal of greater than about 1000 angstroms perminute, or to provide controlled removal of either or both of thosematerials from the wafer surface at a slow to moderate rate of removalof about 50 to about 1000 angstroms per minute. The composition of theinvention is useful in removing low-k dielectrics including, forexample, trimethylsilane- and dimethylsilane-based low-k dielectrics.

[0010] For example, the composition can be formulated for use in aprocessing step such as a post-etch cleaning where it is desirable toremove low-k dielectric material at a slow and controlled rate so as toprovide better process control. In that case, the cleaning compositionis formulated with a relatively dilute concentration of thefluorine-comprising compound. By comparison, in a dummy recyclingoperation after a photoresist deposition or etching step, it is highlydesirable to quickly and completely remove the low-k dielectric materialand any photoresist or other organic components that may be present fromthe surface of the wafer, whereby the surface of the wafer ishydrophobic and water sheets off the surface of a wafer. In that case, arelatively high concentration of fluorine-comprising component is usedin the composition. The composition can also be formulated to removephotoresist from a wafer, for example, after a mask operation, and leavethe underlying low-k dielectric layer intact.

[0011] Suitable fluorine-comprising compounds are those that willspeciate or ionize to provide fluoride ions at about pH 3 to 9. Thefluorine-comprising compound can be an inorganic fluoride compound suchas hydrofluoric acid (HF) and ammonium fluoride (NH₄F), or an organicfluoride compound such as tetramethylammonium fluoride and hydrogenfluoride pyridinium. Combined with the inorganic fluorine-comprisingcompound is an organic acid component that can be one or more of amonobasic, dibasic or tribasic organic acid, and is preferably citricacid, acetic acid, ascorbic acid, or mixtures thereof. An organicfluorine-comprising compound, when used, is combined with an inorganicacid such as sulfuric acid, among others. The acid component is includedin an amount to control the pH of the composition at about 3 to about 9.

[0012] The invention also provides a method of cleaning a surface of awafer. One embodiment of the method includes providing an aqueouscleaning composition that includes at least one fluorine-comprisingcompound and at least one acid component, and has a pH of about 3 toabout 9; providing a wafer having a low-k dielectric layer and anoverlying photoresist layer on at least one surface; and contacting thesurface of the wafer having the low-k dielectric material andphotoresist layers thereon with the cleaning solution under conditionseffective to remove both of the low-k dielectric material and thephotoresist layers substantially completely from the surface of thewafer, at a desired rate of removal whereby the resulting cleanedsurface of the wafer is hydrophobic and water sheets off the surface ofthe wafer.

[0013] Another embodiment of the method includes providing an aqueouscleaning composition that includes at least one fluorine-comprisingcompound and at least one acid component and has a pH of about 3 toabout 9; providing a wafer having a masked or unmasked low-k dielectricmaterial on at least one surface; and contacting the surface of thewafer having the low-k dielectric material thereon with the cleaningsolution under conditions effective to remove at least a portion of thelow-k material at a desired rate of removal.

[0014] A further embodiment of the method includes providing an aqueouscleaning composition that includes at least one fluorine-comprisingcompound and at least one acid, and has a pH of about 3 to about 9;providing a wafer having a low-k dielectric layer and an overlyingphotoresist layer on at least one surface; and contacting the surface ofthe wafer having the low-k dielectric and photoresist layers thereonunder conditions effective to remove the photoresist layer at a desiredrate of removal while leaving the a low-k dielectric layer essentiallyintact.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Preferred embodiments of the invention are described below withreference to the following accompanying drawings which are forillustrative purposes only. Throughout the following views, referencenumerals will be used on the drawings, and the same reference numeralswill be used throughout the several views and in the description toindicate same or like parts.

[0016] FIGS. 1A-1B are general illustrations of cross-section of a waferhaving a layer of a low-k dielectric material and an overlyingphotoresist layer on a surface, before and after cleaning, respectively,to remove both layers from the surface of the wafer in accordance withone embodiment of the method of the present invention.

[0017] FIGS. 2A-2B are general illustrations of cross-section of a waferhaving a layer of an unmasked low-k dielectric material on a surface,before and after cleaning, respectively, to remove the low-k dielectriclayer in accordance with another embodiment of the method of the presentinvention.

[0018] FIGS. 3A-3B are general illustrations of cross-section of a waferhaving a layer of low-k dielectric material and an overlying photoresistlayer on a surface, before and after cleaning, respectively, to removethe photoresist layer from the wafer in accordance with anotherembodiment of the method of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The invention provides improved cleaning of a wafer surface inthe production of semiconductor wafers. Aqueous blends of at least onefluorinated compound and at least one compatible acid are provided thatcan be optimized by task for removal of low-k dielectric material andphotoresist or other organic components from the surface of a wafer.

[0020] In accordance with the present invention, the compositions can beformulated to provide rapid removal of a low-k dielectric material, acontrolled low to moderate rate of removal of a low-k dielectricmaterial, removal of both resist and low-k dielectric materials, and/orremoval of photoresist material with selectivity to low-k dielectricmaterial. The blends are used for removal of a low-k dielectric layerand/or a layer of photoresist or other organic layer with selectivity toan underlying layer of a silicon substrate.

[0021] The fluorine-comprising compound which attacks the low-kdielectric material, is combined with an acid component that assists inthe dissolution of the organic components. The pH of the cleaningcomposition is maintained at an appropriate level by the addition of aneffective amount of the acid component to provide an environment forspeciation of the fluorine-comprising compound to fluorine ions, and toachieve the desired etch selectivity. At a pH >9, free fluorine isavailable only as fluoride ions (F⁻) which has little etching effect onsilicon oxide material. At a pH <3, the available fluorine species aredominantly molecular, i.e., HF and H₂F₂. At an about pH 3.5, there is amixture of species present. Preferably, the pH of the composition ismaintained at a pH of about 3 to about 9 such that the ionic fluorinespecies dominates. By adjusting the pH, the dominant species of fluorine(HF₂ ⁻ in the cleaning composition can be varied to adjust the etch rateon the low-k dielectric material.

[0022] Suitable fluorine-comprising compounds are those that speciateand release fluoride ions at a pH between about 3 to about 9. Examplesof suitable fluorine-comprising compounds, i.e., include inorganicfluorines such as hydrofluoric acid (HF), ammonium fluoride (NH₄F), andmixtures thereof; and organic fluorines such as tetramethylammoniumfluoride, hydrogen fluoride pyridinium, triethylamine trihydrofluoride,and other straight, branched, cyclic or aromatic derivatives, andmixtures thereof.

[0023] In the use of HF, NH₄F, or other inorganic fluorine-comprisingcompound, the acid component is an organic acid. Suitable organic acidsinclude, but are not limited to monobasic acids such as formic, acetic,propionic, n-butyric, isobutyric, and benzoic acid; dibasic acids suchas ascorbic, gluconic, malic, malonic, oxalic, succinic, and tartaricacids; tribasic acids such as citric and gallic acids; and mixturesthereof. In the use of an organic fluorine-comprising compound, asuitable inorganic acid is used, as for example, sulfuric acid,hydrochloric acid, nitric acid and phosphoric acid. The composition istypically in the form of a solution, and includes a solvent, preferablywater, for dilution of the components.

[0024] The cleaning composition includes the fluorine-comprisingcompound and acid component in an amount effective to provide thedesired selectivity and etch rate for removal of low-k dielectricmaterial and/or a polymeric photoresist. Combinations of variousinorganic/organic fluorine-comprising compounds and organic/inorganicacids according to the invention can be used for the desired results.

[0025] A first embodiment of a cleaning composition according to theinvention and a method for its use in cleaning or etching the surface ofa semiconductor wafer, is described with reference to FIGS. 1A-1B.

[0026] Referring to the figures, a portion of a wafer 10 is shown priorto cleaning (FIG. 1A) and after cleaning (FIG. 1B). The wafer 10includes a substrate 12, for example, a silicon substrate, with asurface 14. A layer or film of a low-k dielectric material 16 overliesthe surface 14 of the substrate 12. Overlying the low-k dielectric layer12 are portions of an organic component 18 such as photoresist mask.

[0027] According to the invention a cleaning composition can beformulated to provide complete removal of the photoresist layer 18 andlow-k dielectric layer 16 from the surface 14 of the silicon substrate12. FIG. 1B depicts the portion of the wafer 10 after cleaning, with thelow-k dielectric layer 16 and the photoresist layer 18 having beencompletely removed by the cleaning process, resulting in a hydrophobic,oxide-free silicon surface 14.

[0028] The substantially complete removal of both a low-k dielectricmaterial and a photoresist layer is particularly useful in the recyclingof wafer dummies where it is desired to completely remove all low-kdielectric and organic materials including a photoresist layer from thewafer down to bare silicon to produce a clean surface that ishydrophobic (i.e., water sheets off the surface), for reuse of the waferdummy in production.

[0029] A useful cleaning composition according to the invention for thesubstantially complete removal of a low-k dielectric material and aphotoresist layer or other organic material from the surface of asilicon-comprising semiconductor wafer is an aqueous solution thatincludes an inorganic fluorine-comprising compound such as HF, NH₄F, andmixtures thereof, and an organic acid such as citric acid, among others.

[0030] An example of a preferred composition to remove substantially allof a low-k dielectric material and a layer of photoresist or otherorganic material from the surface of a wafer at a relatively low tomoderate controlled rate of removal of about 50-1000 angstroms perminute to produce a hydrophobic wafer surface, comprises an aqueoussolution of an about 1:2 (v/v) ratio of hydrofluoric acid (HF) and 50%citric acid and/or other organic acid, or about 30 to about 40% byvolume of 49% HF and about 60 to about 70% by volume 50% citric acidand/or other organic acid, based on the total volume of the composition,with a pH of about 3 to about 4, to provide a relatively moderate rateof removal of the dielectric and photoresist layers at about 400 toabout 600 angstroms per minute. Another useful composition comprises anaqueous solution of an about 2:1 ratio (v/v) of 40% ammonium fluoride(NH₄F) and 50% citric acid and/or other organic acid, or about 60 toabout 70% by volume of 40% NH₄F and about 30 to about 40% by volume of50% citric acid and/or other organic acid, based on the total volume ofthe composition, with a pH of about 4 to about 6, to provide arelatively low rate of removal of the low-k dielectric layer at about 50to about 150 angstroms per minute, preferably about 100 angstroms perminute.

[0031] To provide rapid removal of low-k dielectric material at a rategreater than about 1000 angstroms per minute, preferably greater thanabout 2000 angstroms per minute, and minimal removal of a photoresistlayer, a preferred composition is an aqueous solution of 49%hydrofluoric acid (HF) and 50% citric acid and/or other organic acid ina ratio (v/v) of about 2:1, or about 63 to about 70 percent by volume of49% HF and about 30 to about 36 percent by volume of 50% citric acidand/or other organic acid, with a pH of about 2 to about 5, to generallyachieve a removal rate of about 2300-2700 angstroms per minute. Anotheruseful composition for fast removal of a low-k material comprises anaqueous solution of 40% ammonium fluoride (NH₄F) and 50% citric acidand/or other organic acid in a ratio (v/v) of about 2:1, or about 63 toabout 70 percent by volume of 40% NH₄F and about 30 to about 36 percentby volume of 50% citric acid and/or other organic acid, with a pH ofabout 3 to about 6.

[0032] A cleaning composition for substantially complete removal of botha low-k layer and photoresist layer can also be prepared with an organicfluoride such as hydrogen fluoride pyridinium combined with an inorganicacid such as sulfuric acid. A preferred composition comprises an about1:5 ratio (v/v) of hydrogen fluoride pyridinium and 90% sulfuric acid(H₂SO₄), and/or other inorganic acid, or about 13 to about 19% by volumehydrogen fluoride pyridinium and about 80 to about 86% by volume of 90%H₂SO₄ and/or other inorganic acid, to provide a rapid rate of removal ofthe photoresist layer and a rate of removal of the dielectric layer atabout 700 angstroms per minute.

[0033] A second embodiment of a cleaning composition according to theinvention, and a method for its use is described with reference to FIGS.2A-2B. The wafer 30 to be cleaned includes a substrate 12, for example,a silicon substrate, and a surface 14. Overlying the surface 14 of thesubstrate 12 is an unmasked low-k dielectric film or layer 16 having athickness T₁. According to the method, the cleaning composition isapplied to the wafer 30 for removal of at least a portion of the low-kdielectric layer 36 from the surface 34 of the silicon-comprisingsubstrate 32. FIG. 2B depicts the portion of the wafer 30 aftercleaning. As depicted, the thickness T₁, of the low-k dielectric layer36 has been reduced to thickness T₂ by the removal process. The low-kdielectric layer 36 can also be completely removed to produce ahydrophobic, oxide-free silicon surface 34, as depicted in FIG. 1B.

[0034] The foregoing cleaning compositions can be formulated accordingto the invention to provide removal of at least a portion of the low-kdielectric layer 16 from the surface of a semiconductor wafer at a rapidrate of removal (>1000 angstroms per minute) or a more controlled low tomoderate rate of removal (about 50 to about 1000 angstroms per minute).A slow and controlled removal of low-k dielectric films is desirable incases where removing the low-k dielectric material too quickly from thewafer leads to inadequate process control and causes difficulty inprocess integration. This is important when the objective is to removesmall amounts of the low-k dielectric, such as from a silicon contactarea. For example, in a post-etch cleaning, it is desirable toselectively remove a low-k dielectric material from a wafer at a slowand controlled rate in order to remove a small amount of the dielectricmaterial from an etched feature and leave the bulk of the film intact.In that case, a preferred etchant composition is one that is formulatedwith a dilute HF ratio.

[0035] The compositions can be used to selectively remove all or aportion of a masked low-k dielectric layer while leaving the photoresistmask essentially intact. Such a composition is useful where wetpatterning is required (rather than RIE). The composition is formulatedto provide an etch selectively ratio of about 50:1 to about 1000:1 for alow-k dielectric:photoresist whereby the low-k dielectric material isselectively removed without attacking the photoresist or other organicmaterial.

[0036] Another embodiment of a cleaning composition according to theinvention, and a method for its use to remove photoresist from a wafersurface while leaving an underlying low-k dielectric layer essentiallyintact on the wafer surface, is described with reference to FIGS. 3A-3B.A portion of a wafer 40 is shown which includes a substrate 12, forexample, a silicon substrate, with a surface 14. A layer or film of alow-k dielectric material 16 overlies the surface 14 of the substrate12. Overlying the low-k dielectric layer 16 are portions of aphotoresist mask 18. According to the method, a cleaning composition isapplied to a wafer 40 to provide selective removal of substantially allof the photoresist mask layer 18, while leaving the underlying layer oflow-k dielectric layer 16 essentially intact. FIG. 2B depicts theportion of the wafer 40 after cleaning, with the photoresist layer 18having been completely removed by the cleaning process with the low-kdielectric material remaining on the wafer substrate 12.

[0037] This cleaning method is particularly useful for removing aphotoresist layer after an etch processing step, or in a reworkapplication to remove a misaligned resist mask. The composition isformulated to provide an etch selectivity ratio of about 200:1 for alow-k dielectric:photoresist in which the photoresist material isselectively removed at about 200 angstroms/minute without substantiallyattacking the low-k dielectric material, or a rate of removal of up toabout 1 angstrom/minute.

[0038] A useful composition for the sole removal of a photoresist masklayer or other organic layer overlying a low-k dielectric layercomprises an aqueous solution of an inorganic fluorine-comprisingcompound and a major amount of an organic acid such as a 50% citricacid, with a pH of about 3 to about 4. A preferred composition comprisesan about 1:100 (v/v) of an inorganic fluorine-comprising compound and anabout 20 to about 60%, preferably about 40% to about 50%, aqueoussolution of an organic acid. Preferably, the inorganicfluorine-comprising compound is included in an amount of up to about 2%by volume, preferably about 0.5% to about 1.5% by volume, and theorganic acid is included in an amount of up to about 5 99.5% by volume,preferably about 98.5% to about 99.5% by volume, based on the totalvolume of the composition, with a pH of about 3 to about 3.5. Apreferred composition comprises an about 1:100 ratio of 49% HF and 50%citric acid and/or other organic acid, which provides a rate of removalof the photoresist layer at about 400-600 angstroms per minute with anetch selectivity for a low-k material relative to a polymericphotoresist material of at least about 200:1.

[0039] To clean a wafer surface according to the invention, the wafer isplaced in contact with an appropriately formulated cleaning compositionto remove the desired layer or layers at a desired rate of removal. Thecleaning composition can be applied using a conventional wet chemicalapplication technique as known and used in the art. For example, one ormore wafers can be placed vertically in a carrier or boat and thensubmerged in a recirculating bath of the cleaning composition, with orwithout agitation for about 5-10 minutes, depending on the thickness ofthe layer to be removed. The cleaning composition can also be sprayedonto the surface of the wafer. Preferably, a substantially constantconcentration of the reactive components of the cleaning composition isbrought into contact with the wafer surface so that a uniform rate ofremoval can be maintained to allow for process uniformity and thedesired extent and completeness of removal.

[0040] In the cleaning of a wafer, the cleaning composition can be usedat a temperature of about 15° C. to about 30° C., preferably at about15° C. to about 30° C. High temperatures of about 40 to about 60° C. canbe typically used to achieve faster etch rates. In a selective removalof a photoresist mask or other organic material and not a low-kdielectric layer, it is preferred that lower temperatures of about 15°C. to about 30° C. are used to improve the selectivity of the low-kdielectric material over the photoresist.

[0041] Depending on the composition of the cleaning composition, otherselective etch ratios/rates are within the scope of the presentinvention. The selectivity and removal time can be adjusted andcontrolled by varying the concentrations of the fluorine-comprisingcompound and the acid component, as further illustrated in the examples.The selectivities vary as the v/v ranges increase and decrease.Generally, a composition formulated to comprise a major amount pf HFwill provide a high etch of the low-k dielectric material selective tothe resist. With a major amount of the acid component and a lowercontent of the fluorine-comprising compound, good removal of the resistselective to the low-k dielectric material will be achieved.

[0042] The following examples are given to illustrate specific preferredembodiments of the present invention. Numerous other variations,however, are within the scope of the present invention.

EXAMPLE

[0043] This example studies the effect of varying thefluorine-comprising component (49%HF of 40% NH₄F), and the v/v ratios ofthe fluorine-comprising component and the acid component (50% citricacid) on the rate of removal of a low-k dielectric and a photoresistlayer (OIR 897-101) from a silicon wafer surface. TABLE 1 Low-k FluorineAcid removal rate Photoresist Run # component Parts (v) Component Parts(v) (Å/min.) Removal 1 49% HF 100 — — ^(a)negligible ^(a)negligible 249% HF 100 — — ^(b)negligible ^(b)negligible 3 40% NH₄F 2 50% citricacid 1  100 negligible 4 49% HF 2 50% citric acid 1 2500 negligible 549% HF 1 50% citric acid 2  500 complete 6 49% HF 1 50% citric acid  100Negligible complete 7^(c) Hydrogen 1 90% sulfuric acid 5 Complete (700)Complete fluorine pyridinium (anhydride)

[0044] The surface of the wafers had a layer of chemical vapor deposited(CVD) trimethylsilane-based low-k dielectric film (TMS delivered in H₂and N₂O) about 3000 angstroms thick, and an overlying layer ofphotoresist. The wafers were immersed in a beaker of the cleaningsolution. Run Nos. 3-6 were immersed in solution for multiple tests,from 30 seconds to 4 minutes. The low-k dielectric removal rates weredetermined by using a UV1250 spectroscopic ellipsometer.

[0045] The results show that changing the fluorine-comprising component,and varying the amounts of the fluorine and acid components alters therate of removal of a layer of low-k from the wafer surface.

[0046] The results of Run Nos. 1-2 show that HF used alone wasineffective in removing dielectric and photoresist material from thewafer surface. The use of HF alone resulted in pieces of the TMS-basedlow-k dielectric film and photoresist flaking off and floating on thesurface of the cleaning solution, without significant dissolution.

[0047] The results of Runs 3 and 4 show the effect of varying theinorganic fluorine component that is used on the rate of removal of theTMS-based low-k dielectric layer. A 2:1 of NH₄F:citric acid provided alow-k dielectric removal rate of about 100 angstroms per minute, while a2:1 of HF: citric acid provided a low-k dielectric removal rate of about2500 angstroms per minute.

[0048] The results of Run Nos. 4-6 show the effect of varying the weightratio of the organic acid (50% citric acid) and the fluorine component(HF) on the rate of removal of the TMS-based low-k dielectric film and apolymeric photoresist mask layer from the surface of the wafer. A 1:100HF:citric acid ratio resulted in complete removal of the photoresistwhile leaving the low-k layer intact on the surface of the wafer. A 1:2HF:citric acid ratio resulted in complete removal of both thephotoresist and the TMS-based low-k dielectric film layers, with amoderate rate of removal of the low-k layer at about 500 angstroms perminute. A 2:1 ratio of HF:citric acid ratio resulted in rapid removal ofTMS-based low-k dielectric film at about 2500 angstroms per minute, andnegligible removal of photoresist.

[0049] In compliance with the statute, the invention has been describedin language more or less specific as to structural and methodicalfeatures. It is to be understood, however, that the invention is notlimited to the specific features shown and described, since the meansherein disclosed comprise preferred forms of putting the invention intoeffect. The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents. The disclosure of cited patents are incorporated byreference herein.

What is claimed is:
 1. A method of cleaning wafer surfaces, comprisingthe steps of: providing a wafer surface bearing overlying materialthereon; and cleaning the wafer surface by removing at least a portionof the overlying material from the wafer surface by applying an aqueoussolution comprising a major amount of one or more inorganicfluorine-comprising compounds and one or more organic acids in a ratioof about 100:1 to about 55:45, the solution having a pH of about 3 toabout 9, such that the surface of the wafer is rendered substantiallyhydrophobic.
 2. The method of claim 3, wherein the overlying material onthe surface of the wafer comprises a low-k dielectric layer, and thestep of cleaning the wafer surface comprises removing the dielectriclayer at a rate of greater than about 1000 angstroms per minute.
 3. Themethod of claim 2, wherein the aqueous solution comprises one or morehydrofluoric acid and one or more organic acids in a ratio of about 2:1(v/v), such that the dielectric layer is removed at a rate of about 2500angstroms per minute.
 4. The method of claim 2, wherein the aqueoussolution comprises at least ammonium fluoride and one or more organicacids in a ratio of about 2:1 (v/v).
 5. The method of claim 1, whereinthe overlying material on the surface of the wafer comprises a low-kdielectric layer, and the step of cleaning the wafer surface comprisesremoving the dielectric layer from the wafer surface at a rate of about50 to about 1000 angstroms per minute.
 6. The method of claim 5, whereinthe aqueous solution comprises at least hydrofluoric acid and one ormore organic acids in a ratio of about 1:2 (v/v), such that thedielectric layer is removed at a rate of about 400 to about 600angstroms per minute.
 7. The method of claim 5, wherein the aqueoussolution comprises at least ammonium fluoride and one or more organicacids in a ratio of about 2:1, such that the dielectric layer is removedat a rate of about 50-150 angstroms per minute.
 8. The method of claim1, wherein the overlying material on the surface of the wafer comprisesa low-k dielectric layer, and a photoresist layer overlying thedielectric layer and the step of cleaning the wafer surface comprisesremoving the dielectric layer and the photoresist layer at a rate ofabout 50 to about 1000 angstroms per minute.
 9. The method of claim 8,wherein the aqueous solution comprises at least hydrofluoric acid andone or more organic acids in a ratio of about 1:2 (v/v), such that thedielectric layer is removed at a rate of about 400 to about 600angstroms per minute.
 10. The method of claim 9, wherein the aqueoussolution comprises at least ammonium fluoride and one or more organicacids in a ratio of about 2:1 (v/v), such that the dielectric layer isremoved at a rate of about 100 angstroms per minute.
 11. The method ofclaim 1, wherein the composition is an aqueous solution consistingessentially of the one or more in organic fluorine-comprising compoundsand the one or more organic acids.
 12. A method for surface treatingwafer surfaces, comprising the steps of: providing a wafer surfacehaving a low-k dielectric layer disposed thereon and a photoresist layeroverlying the dielectric layer; and treating the wafer surface to removeat least a portion of the dielectric layer with minimal removal of thephotoresist layer, by applying an aqueous solution of one or moreinorganic fluorine-comprising compounds and one or more organic acids,the solution having a pH of about 3 to about 9, such that the dielectriclayer is removed selective to the photoresist at a rate of greater thanabout 1000 angstroms per minute.
 13. The method of claim 12, wherein theaqueous solution comprises at least hydrofluoric acid and the one ormore organic acids in a ratio of about 2:1 (v/v), such that thedielectric layer is selectively removed at a rate of about 2300 to about2700 angstroms per minute.
 14. The method of claim 12, wherein theaqueous solution comprises at least ammonium fluoride and the one ormore organic acids in a ratio of about 2:1 (v/v).
 15. A method forsurface treating wafer surfaces, comprising the steps of: providing awafer surface having a low-k dielectric layer disposed thereon and aphotoresist layer overlying the dielectric layer; and treating the wafersurface to remove at least a portion of the dielectric layer withminimal removal of the photoresist layer, by applying an aqueoussolution of one or more inorganic fluorine-comprising compounds and oneor more organic acids in a ratio of about 1:2 (v/v), and having a pH ofabout 3 to about 9 such that the dielectric layer is removed selectiveto the photoresist at a rate of about 50 to about 1000 angstroms perminute.
 16. The method of claim 15, wherein the aqueous solutioncomprises at least hydrofluoric acid, and the dielectric layer isselectively removed at a rate of about 400 to about 600 angstroms perminute.
 17. The method of claim 15, wherein the aqueous solutioncomprises at least ammonium fluoride and the one or more organic acidsin a ratio of about 2:1 (v/v), such that the dielectric layer isselectively removed at a rate of about 50 to about 150 angstroms perminute.
 18. A post-etch cleaning to selectively remove a low-kdielectric material from a wafer, comprising: providing a wafer surfacehaving a layer of the low-k dielectric material disposed thereon and aphotoresist layer overlying the dielectric layer; and treating the wafersurface to remove at least a portion of the dielectric layer, by applyan aqueous solution of a least one inorganic fluorine-comprisingcompound and at least one organic acid component in a ratio of about 1:2(v/v), the solution having a pH of about 3 to about 9, such that theremoval rate of the low-k dielectric material is controlled at about 50to about 1000 angstroms per minute.
 19. A method of cleaning wafersurfaces, the method comprising the steps of: providing an aqueoussolution comprising at least one inorganic fluorine-comprising compoundand at least one organic acid; providing a wafer having an unmaskedlow-k dielectric material disposed on at least a portion of one surface;and contacting the surface of the wafer having the low-k dielectricmaterial thereon with the aqueous solution under conditions effective toremove at least a portion of the low-k dielectric material at a rate ofgreater than about 1000 angstroms per minute.
 20. A method of cleaningwafer surfaces, the method comprising the steps of: providing an aqueoussolution comprising at least one inorganic fluorine-comprising compoundselected from the group consisting of hydrofluoric acid and ammoniumfluoride, and mixtures thereof; and at least one organic acid selectedfrom the group consisting of citric acid, acetic acid, ascorbic acid,and mixtures thereof; providing a wafer having a low-k dielectricmaterial disposed on at least a portion of one surface; and contactingthe surface of the wafer having the low-k dielectric material thereonwith the aqueous solution under conditions effective to remove at leasta portion of the low-k dielectric material at a rate of about 50 toabout 1000 angstroms per minute.
 21. The method of claim 20, wherein theaqueous solution comprises about 30% to about 70% by volume of thefluorine-comprising compound, and about 30% to about 70% by volume ofthe organic acid, based on the total volume of the solution.
 22. Themethod of claim 20, wherein the aqueous solution includes at leasthydrofluoric acid and at least one organic acid in a ratio of about 1:2(v/v), to remove at least a portion of the low-k material at a rate ofabout 400 to about 600 angstroms per minute.
 23. The method of claim 22,wherein the aqueous solution includes about 30 to about 40% by volume ofhydrofluoric acid, and about 60 to about 70% by volume of the organicacid.
 24. The method of claim 20, wherein the aqueous solution includesat least ammonium fluoride and at least one organic acid in a ratio ofabout 2:1 (v/v), to remove at least a portion of the low-k material at arate of about 50 to about 150 angstroms per minute.
 25. The method ofclaim 24, wherein the aqueous solution includes about 60 to about 70% byvolume of ammonium fluoride, and about 30 to about 40% by volume of theorganic acid.
 26. A method of cleaning wafer surfaces, the methodcomprising the steps of: providing an aqueous solution comprising aninorganic fluorine-comprising compound selected from the groupconsisting of hydrofluoric acid and ammonium fluoride, and mixturesthereof; and an organic acid selected from the group consisting ofcitric acid, acetic acid, ascorbic acid, and mixtures thereof; providinga wafer having a low-k dielectric material disposed on at least aportion of one surface; and contacting the surface of the wafer havingthe low-k dielectric material thereon with the aqueous solution underconditions effective to remove at least a portion of the low-kdielectric material at a rate greater than about 1000 angstroms perminute.
 27. The method of claim 26, wherein the aqueous solutionincludes at least hydrofluoric acid and one or more organic acids in aratio of about 2:1 (v/v).
 28. The method of claim 27, wherein theaqueous solution includes about 63 to about 70% by volume ofhydrofluoric acid, and about 30 to about 36% by volume of the one ormore organic acids.
 29. The method of claim 26, wherein the aqueoussolution includes at least ammonium fluoride and one or more organicacids in a ratio of about 2:1 (v/v).
 30. The method of claim 26, whereinthe aqueous solution includes about 63 to about 70% by volume ofammonium fluoride, and about 30 to about 36% by volume of the one ormore organic acids.
 31. A method of surface treating wafer surfaces,comprising the steps of: providing a wafer surface having a low-kdielectric layer disposed thereon and a photoresist layer overlying thedielectric layer; and providing an aqueous composition comprising atleast one inorganic fluorine-comprising compound, and a major amount ofone or more organic acids; and contacting the surface of the waferhaving the low-k dielectric and photoresist layers thereon with thecomposition under conditions effective to selectively remove thephotoresist layer while leaving the low-k layer essentially intact onthe substrate.
 32. The method of claim 31, wherein the compositioncomprises an aqueous solution of at least hydrofluoric acid and the oneor more organic acids in a ratio of about 1:100 to about 45:55 (v/v),such that the composition removes the photoresist mask completely fromthe surface selective to the dielectric layer.
 33. The method of claim31, wherein the inorganic fluorine-comprising compound is selected fromthe group consisting of hydrofluoric acid, ammonium fluoride, andmixtures thereof; and the organic acid is selected from the groupconsisting of citric acid, gallic acid, acetic acid, formic acid,propionic acid, n-butyric acid, isobutyric acid, benzoic acid, ascorbicacid, gluconic acid, malic acid, malonic acid, oxalic acid, succinicacid, tartaric acid, and mixtures thereof.
 34. The method of claim 31,wherein the organic acid is selected from the group consisting of citricacid, acetic acid, ascorbic acid, and mixtures thereof.
 35. The methodof claim 31, wherein the step of contacting the surface of the wafercomprises immersing the wafer in a bath of the composition, spraying thesurface of the wafer with the composition, exposing the wafer to avapor, or any combination thereof.
 36. A method of cleaning wafersurfaces, comprising: formulating an aqueous composition for selectivelyremoving at least a portion of a low-k dielectric layer from a wafersurface at a predetermined rate, the composition consisting essentiallyof one or more inorganic fluorine-comprising compounds and one or moreorganic acids, and having a pH of about 3 to about 9; providing a waferhaving a low-k dielectric material disposed on at least a portion of onesurface; and contacting the wafer having the low-k dielectric materialthereon with the composition under conditions effective to remove atleast a portion of the low-k dielectric material at the predeterminedrate.
 37. The method of claim 36, wherein the inorganicfluorine-comprising compound is selected from the group consisting ofhydrofluoric acid, ammonium fluoride, and mixtures thereof; and theorganic acid is selected from the group consisting of citric acid,acetic acid, ascorbic acid, and mixtures thereof.
 38. The method ofclaim 36, wherein the composition is formulated to remove the dielectriclayer at a rate greater than about 1000 angstroms per minute.
 39. Themethod of claim 36, wherein the composition is formulated to remove thedielectric layer at a rate of about 50 to about 1000 angstroms perminute.
 40. The method of claim 36, wherein at least a portion of thelow-k dielectric layer is unmasked.
 41. The method of claim 36, whereinat least a portion of the low-k dielectric layer is masked by anoverlying layer of photoresist.
 42. The method of claim 41, wherein thecomposition is formulated to remove the dielectric layer and thephotoresist layer from the surface of the wafer, such that the surfaceof the substrate is rendered substantially hydrophobic.
 43. The methodof claim 41, wherein the composition is formulated to remove thedielectric layer selective to the photoresist at a rate of about 50 toabout 1000 angstroms per minute.
 44. The method of claim 41, wherein thecomposition is formulated to remove the dielectric layer selective tothe photoresist at a rate of greater than about 1000 angstroms perminute.
 45. A method of cleaning wafer surfaces, comprising: formulatingan aqueous composition for selectively removing at least a portion of alow-k dielectric layer disposed on the wafer surface at a predeterminedrate, the composition consisting essentially of one or more organicfluorine-comprising compounds and one or more inorganic acids, andhaving a pH of about 3 to about 9; providing a wafer having a low-kdielectric material disposed on at least a portion of one surface; andcontacting the wafer having the low-k dielectric material thereon withthe composition under conditions effective to remove at least a portionof the low-k dielectric material at the predetermined rate.
 46. Themethod of claim 45, wherein the organic fluorine-comprising compound isselected from the group consisting of hydrogen fluoride pyridinium,triethylamine trihydrofluoride, tetramethylammonium fluoride, andmixtures thereof.
 47. The method of claim 45, wherein the inorganic acidis selected from the group consisting of sulfuric acid, nitric acid,hydrochloric acid, phosphoric acid, and mixtures thereof.
 48. The methodof claim 45, wherein the composition is formulated to remove thedielectric layer at a rate greater than about 1000 angstroms per minute.49. The method of claim 45, wherein the composition is formulated toremove the dielectric layer at a rate of about 50 to about 1000angstroms per minute.
 50. The method of claim 45, wherein at least aportion of the low-k dielectric layer is unmasked.
 51. The method ofclaim 45, wherein at least a portion of the low-k dielectric material ismasked by an overlying layer of photoresist.
 52. The method of claim 51,wherein the composition is formulated to remove the dielectric layer andthe photoresist layer from the surface of the wafer such that thesurface of the substrate is rendered substantially hydrophobic.
 53. Themethod of claim 51, wherein the composition is formulated to remove thedielectric layer selective to the photoresist at a rate of about 50 toabout 1000 angstroms per minute.
 53. The method of claim 51, wherein thecomposition is formulated to remove the dielectric layer selective tothe photoresist at a rate of greater than about 1000 angstroms perminute.
 54. A composition for cleaning or treating a surface of asemiconductor wafer, comprising: an aqueous solution of a major amountof one or more inorganic fluorine-comprising compounds and one or moreorganic acids in a ratio of about 100:1 to about 55:45 (v/v), to removeorganic material and low-k dielectric material from the surface of thewafer whereby the surface of the substrate is rendered substantiallyhydrophobic; the composition having a pH of about 3 to about
 9. 55. Thecomposition of claim 54, wherein the inorganic fluorine-comprisingcompound is selected from the group consisting of hydrofluoric acid,ammonium fluoride, and mixtures thereof.
 56. The composition of claim54, wherein the organic acid is selected from the group consisting ofcitric acid, gallic acid, acetic acid, formic acid, propionic acid,n-butyric acid, isobutyric acid, benzoic acid, ascorbic acid, gluconicacid, malic acid, malonic acid, oxalic acid, succinic acid, tartaricacid, and mixtures thereof.
 57. The composition of claim 54, wherein theorganic acid is selected from the group consisting of citric acid,acetic acid, ascorbic acid, and mixtures thereof.
 58. The composition ofclaim 54, wherein the aqueous solution consists essentially of the oneor more inorganic fluorine-comprising compounds and the one or moreorganic acids.
 59. The composition of claim 54, wherein the aqueoussolution includes at least hydrofluoric acid and at least one organicacid in a ratio of about 1:2 (v/v).
 60. The composition of claim 59,wherein the aqueous solution includes about 30 to about 40% by volume ofhydrofluoric acid, and about 60 to about 70% by volume of the organicacid.
 61. The composition of claim 54, wherein the aqueous solutionincludes at least ammonium fluoride and at least one organic acid in aratio of about 2:1 (v/v).
 62. The composition of claim 61, wherein theaqueous solution includes about 60 to about 70% by volume of ammoniumfluoride, and about 30 to 40% by volume of the organic acid.
 63. Acomposition for cleaning or treating a surface of a semiconductor wafer,comprising: an aqueous solution of a major amount of one or more organicfluorine-comprising compounds and one or more inorganic acids in a ratioof about 1:5 (v/v), to remove organic material and low-k dielectricmaterial from the surface of the wafer such that the surface of thesubstrate is rendered substantially hydrophobic; the composition havinga pH of about 3 to about
 9. 64. The composition of claim 63, wherein theorganic fluorine-comprising compound is selected from the groupconsisting of hydrogen fluoride pyridinium, tetramethylammoniumfluoride, triethylamine trihydrofluoride, and mixtures thereof.
 65. Thecomposition of claim 63, wherein the inorganic acid is selected from thegroup consisting of sulfuric acid, nitric acid, hydrochloric acid,phosphoric acid, and mixtures thereof.
 66. The composition of claim 63,wherein the aqueous solution consists essentially of the one or moreorganic fluorine-comprising compounds and the one or more inorganicacids.
 67. A composition for surface treating wafer surfaces,comprising: an aqueous solution of a major amount of one or moreinorganic fluorine-comprising compounds and one or more organic acids toremove organic material and low-k dielectric material from the surfaceof the wafer, such that the dielectric layer is removed selective to thephotoresist at a rate of about 50 to about 1000 angstroms per minute;the composition having a pH of about 3 to about
 9. 68. The compositionof claim 67, wherein the aqueous solution comprises at leasthydrofluoric acid, and the dielectric layer is selectively removed at arate of about 400 to about 600 angstroms per minute.
 69. The compositionof claim 67, wherein the aqueous solution comprises at least ammoniumfluoride and the one or more organic acids in a ratio of about 2:1(v/v), such that the dielectric layer is selectively removed at a rateof about 50 to about 150 angstroms per minute.
 70. The composition ofclaim 67, wherein the composition is an aqueous solution consistingessentially of the one or more in organic fluorine-comprising compoundsand the one or more organic acids.
 71. A composition for surfacetreating wafer surfaces, comprising: an aqueous solution of a majoramount of one or more inorganic fluorine-comprising compounds and one ormore organic acids to remove organic material and low-k dielectricmaterial from the surface of the wafer, such that the dielectric layeris removed selective to the photoresist at a rate up to than about 1000angstroms per minute; the composition having a pH of about 3 to about 9.72. The composition of claim 71, wherein the aqueous solution comprisesat least hydrofluoric acid and the one or more organic acids in a ratioof about 1:2 (v/v), whereby the dielectric layer is selectively removedat a rate of about 400 to about 600 angstroms per minute.
 73. Thecomposition of claim 71, wherein the aqueous solution comprises at leastammonium fluoride and the one or more organic acids in a ratio of about2:1 (v/v), whereby the dielectric layer is selectively removed at a rateof about 50 to about 150 angstroms per minute.
 74. The composition ofclaim 71, wherein the composition is an aqueous solution consistingessentially of the one or more in organic fluorine-comprising compoundsand the one or more organic acids.